The IP Multimedia Subsystem (IMS) is a new core network domain defined by the 3GPP in the UMTS R5 and later versions, in which a domain is a new mobile network system composed of more than one Network Element (NE). A prominent characteristic of the IMS is that the Session Initiation Protocol (SIP) is used massively to define key NEs and the capabilities and interfaces of the key NEs. For example, the Proxy Call Section Control Function (P-CSCF), Interrogating Call Session Control Function (I-CSCF), and Service Call Session Control Function (S-CSCF) may be regarded as different types of SIP proxies/servers. The Application Server (AS) that provides services is also based on the SIP.
In the process of research, the inventors find that the type and quantity of services are limited in the conventional technology where both the header and the body of the SIP message carry routing information to realize the service triggering capability of the SIP, and the type is limited to voice services. In the conventional technology, the intention of the calling party is represented by carrying some keywords. However, the relevant devices in the IMS network are unable to understand the meaning of the keywords, and, hence, unable to implement auto discovery or invocation of services for users. Consequently, the type and quantity of the services available are restricted by the quantity of keywords. Moreover, different users may use different keywords, which is unfavorable for mass application.
The coupling relationship between the IMS network and the service is unfavorable for dynamic publication of services and dynamic subscription and access to services. A user can only choose to subscribe to the relevant specific service statically, and is unable to subscribe to services as required.